The present invention relates to an apparatus and method for implementing temperature control on a means for heating.
Various types of semiconductor manufacturing apparatuses having a heater are used in the process of manufacturing a semiconductor device. For instance, heaters are provided at a process chamber wall, a stage on which a semiconductor wafer (hereafter referred to as a xe2x80x9cwaferxe2x80x9d) is placed and the like in a thermal CVD (film forming) device. Thus, in the thermal CVD device, film formation processing is implemented after heating the process chamber wall and the stage to a specific temperature with the heaters. In addition, temperature control of the heaters is implemented by a temperature control apparatus. The temperature control apparatus compares the set temperature and the temperature at a heater detected by a thermal (temperature) sensor. Then, the temperature control apparatus implements on/off control of the power supplied to the heater through switching so as to set the two temperatures roughly equal to each other through an adjustment of the quantity of heat generated by the heater. In addition, an interlocking thermal sensor (hereafter referred to as an xe2x80x9cinterlock sensorxe2x80x9d) is connected to the temperature control apparatus. The temperature control apparatus stops power supply to a heater if the temperature of the heater detected by the interlock sensor indicates a level equal to or higher than the temperature upper limit set at the temperature control apparatus.
However, in the prior art described above, it is necessary to provide a thermal sensor and an interlock sensor in correspondence to each heater. For this reason, if there are a plurality of heaters, the number of individual types of sensors and the wirings required to connect the sensors to the temperature control apparatus are bound to increase in correspondence to the number of heaters. As a result, a problem arises in the prior art in that a large initial cost must be incurred since a great number of sensors must be provided.
In addition, there is another problem in the prior art technology in that the maintainability of the apparatus is lowered due to the complex and time-consuming inspection and testing process that must be conducted on the sensors and the wirings.
In the prior art, the apparatus is bound to be large because of the large numbers of sensors and wirings. Consequently, there is a problem in that the technological requirement for miniaturizing devices such as the CVD device provided in the clean room cannot be met.
Furthermore, the temperature at a heater cannot be directly detected in the prior art. Thus, the heater temperature cannot be ascertained accurately, to lead to a problem of unstable heater temperature control.
In the prior art technology, even when heating a single member by using a plurality of heaters, the temperatures at the individual heaters are sustained at levels roughly equal to one another regardless of the positions at which the heaters are installed. As a result, mutual interference occurs between the heat generated at a given heater and the heat generated at another heater, thereby presenting a problem in that uniformity is not achieved with regard to the temperature of the member.
Moreover, the temperature of a heater is adjusted by supplying power at a specific level to the heater through on/off control implemented on the power in the prior art. This results in a problem in that accurate temperature control cannot be achieved since there is a great difference in the heater temperature when power is on and the heater temperature when power is off and the heater temperature is not sustained at a constant level.
The object of the present invention, which has been completed by addressing the problems of the prior art discussed above, is to provide a new and improved apparatus and a new and improved method for implementing temperature control on a means for heating, that solve the problems discussed above and other problems as well.
In order to achieve the object described above, in a first aspect of the, present invention, a temperature control apparatus that implements temperature control on a means for heating which heats an object to be heated, comprising at least two means for heating each with the resistance thereof increasing as the temperature rises, at least one means for temperature detection that detects the temperature of the object to be heated, a means for target resistance calculation that calculates a target resistance for each of the means for heating by correcting a reference resistance determined based upon the set temperature for the object to be heated with a correction value obtained in correspondence to the temperature detected by the means for temperature detection and multiplying the corrected reference resistance by a temperature distribution constant that is determined in advance for each means for heating to adjust the temperature distribution at the object to be heated, a means for actual resistance calculation that determines the actual resistance at each of the means for heating based upon a feedback voltage value obtained based upon the voltage applied to the means for heating and a feedback current value obtained based upon the current flowing through the means for heating and, a means for power control that controls the power applied to each means for heating so that the actual resistance at the means for heating conforms to the target resistance, is provided.
According to the present invention, means for heating each having a resistance that increases in proportion to an increase in temperature are utilized. As a result, the temperature at each means for heating can be ascertained based upon the actual resistance determined in correspondence to the feedback voltage value and the feedback current value obtained from the means for heating. Thus, the need for providing a means for temperature detection that detects the temperature at a means for heating and a means for connection such as a wiring that connects the means for temperature detection to the temperature control device for each means for heating is eliminated. Consequently, even when heating the object to be heated by utilizing a plurality of means for heating, the initial cost can be minimized and, at the same time, the maintenance work is facilitated. Furthermore, since the temperature at each means for heating can be directly detected, accurate and stable temperature control can be implemented on the means for heating.
In addition, according to the present invention, the reference resistance used as the reference value when implementing control on each means for heating is corrected by using a correction value obtained in correspondence to the temperature detected by the means for temperature detection. By adopting such a structure, it becomes possible to control each means for heating based upon the actual temperature of the object to be heated as well as based upon the set temperature, is provided. As a result, even more accurate temperature control on the individual means for heating is achieved to set the temperature of the object to be heated even closer to the set temperature. Furthermore, according to the present invention, the target resistance is obtained by multiplying the corrected reference resistance by a temperature distribution constant that is provided to adjust the temperature distribution of the object to be heated. When such a target resistance is adopted, the temperatures of the means for heating can be adjusted in conformance to the temperature levels at the individual portions of the object to be heated. Thus, the temperature of the object to be heated can be maintained in an even more consistent manner. Moreover, the ratio of the temperatures of the individual means for heating can be adjusted so as to achieve uniformity in the temperature of the entire object to be heated in this structure. As a result, accurate temperature management is achieved for the object to be heated. The actual resistance at each means for heating is calculated by the means for actual resistance calculation. Consequently, the change in the value of each actual resistance can be ascertained almost concurrently while the change in the temperature at the corresponding means for heating is detected. Thus, an improvement in the response of the means for heating is achieved.
It is desirable to employ a means for phase control that implements phase control on the power applied to the individual means for heating as the means for power control. In such a structure, by changing the phase of the AC power applied to the means for heating as appropriate, the temperatures at the means for heating can be adjusted. As a result, finer control on the means for heating is achieved compared to on/off power control implemented through a means for interruption such as a switch. Consequently, the temperature of the object to be heated is stabilized.
Through the means for phase control, the length of time over which power is applied should be increased if the actual resistance is lower than the target resistance, the current length of power application should be sustained if the actual resistance is essentially equal to the target resistance and the length of time over which power is applied should be reduced if the actual resistance is higher than the target resistance, to achieve a prompt and reliable adjustment of the temperature of the means for heating.
Alternatively, it is desirable to employ a means for zero cross control that implements zero cross control on the power applied to the individual means for heating as the means for power control. In this structure in which power on/off is implemented when the voltage is at zero, noise occurs less readily in the power. As a result, the power is supplied to the means for heating in a stable manner, to further stabilize the temperature of the means for heating.
As a further alternative, the means for power control may be constituted of a means for linear control that implements linear control on the power applied to the means for heating. By adopting such a structure, the power can be controlled continuously. As a result, better control is achieved on each of the means for heating. Furthermore, since noise does not occur readily in the power, stable temperature control is achieved.
It is desirable to connect a means for power supply suspension that suspends the power supply to a means for heating if the actual resistance becomes higher than a resistance upper limit or becomes lower than a resistance lower limit. By adopting such a structure, it becomes possible to detect an error at a means for heating or the like based upon the individual resistance values. Thus, the need for providing a means for temperature detection that detects an abnormality in the temperature and a wiring for connecting the means for temperature detection to the temperature control apparatus is eliminated. As a result, a further reduction in the initial cost and a further improvement in the maintainability are achieved.
The present invention achieves particularly outstanding advantages when adopted in an application in which the object to be heated is a member constituting a semiconductor manufacturing apparatus or the like. In the process for manufacturing a semiconductor device, more accurate temperature control must be achieved in order to support ultra-miniaturization and ultra-high integration of the semiconductor device. Thus, by adopting the present invention in the temperature control of the member that needs to be heated, a higher degree of accuracy in temperature control is achieved. In addition, a semiconductor manufacturing apparatus or the like is often installed in a clean room. Accordingly, by employing the means for heating and the temperature control apparatus in a semiconductor manufacturing apparatus and the like, miniaturization of the apparatus can be achieved since the numbers of various means for temperature detection and the numbers of the means for connection are reduced. As a result, the space inside the clean room can be utilized efficiently or the size of the clean room itself can be reduced. It is to be noted that the semiconductor manufacturing apparatus and the like in this context includes all the devices used during the semiconductor manufacturing process such as various devices connected to the semiconductor manufacturing apparatus as well as the semiconductor manufacturing apparatus itself.
In a second aspect of the present invention, a temperature control apparatus that implements temperature control on a means for heating which heats an object to be heated, comprising at least two means for heating each with the resistance thereof increasing as the temperature rises, at least one means for temperature detection that detects the temperature of the object to be heated, a means for target voltage calculation that calculates a target voltage for each of the means for heating by correcting a reference voltage determined based upon the set temperature for the object to be heated with a correction value obtained in correspondence to the temperature detected by the means for temperature detection and multiplying the corrected reference resistance by a temperature distribution constant that is determined in advance for each means for heating to adjust the temperature distribution at the object to be heated, a means for voltage detection that detects the actual voltage applied to each of the means for heating and, a means for power control that controls the power applied to each means for heating so that the actual voltage at the means for heating conforms to the target voltage, is provided.
According to the present invention, each means for heating is controlled based upon the target voltage value and the actual voltage.
The actual voltage can be obtained by detecting the voltage applied to the means for heating without having to perform any arithmetic operation. As a result, it is not necessary to provide a means for actual voltage calculation or to implement an arithmetic operation step to calculate the actual voltage, thereby achieving simplification of the apparatus configuration and also simplification of the control process.
As in the first aspect of the invention, it is desirable to employ a means for phase control that implements phase control on the power applied to the individual means for heating as the means for power control. As in the first aspect of the invention, through the means for phase control, the length of time over which power is applied should be increased if the actual voltage is lower than the target voltage, the current length of power application should be sustained if the actual voltage is essentially equal to the target resistance and the length of time over which power is applied should be reduced if the actual voltage is higher than the target voltage.
As a desirable alternative, the means for power control may be constituted of a means for zero cross control that implements zero cross control on the power applied to each means for heating or a means for linear control that implements linear control on the power applied to each means for heating, as explained in reference to the first aspect of the invention.
As in the first aspect of the invention, it is desirable to connect a means for power supply suspension that suspends the power supply to a means for heating if the actual voltage becomes higher than the voltage upper limit or becomes lower than the voltage lower limit.
In addition, it is desirable to adopt the present invention in an application in which the object to be heated is a member constituting a semiconductor manufacturing apparatus and the like, as explained in reference to the first aspect of the invention.
In a third aspect of the present invention, a temperature control method to be implemented on a means for heating that heats an object to be heated comprising a step in which a reference resistance determined based upon the set temperature for the object to be heated is corrected by using a correction value obtained in correspondence to the temperature at the object to be heated detected by, at least, one means for temperature detection, a step in which the corrected reference resistance is multiplied by a temperature distribution constant used to adjust the temperature distribution of the object to be heated, which is determined in advance for each of at least two means for heating each with a resistance that increases in correspondence to a temperature increase, to obtain a target resistance for each of the means for heating, a step in which the actual resistance at each of the means for heating is ascertained based upon a feedback voltage which corresponds to the voltage applied to each means for heating and a feedback current value which corresponds to the current flowing through the means for heating and a step in which the power applied to each of the means for heating is controlled so that the actual resistance at the means for heating conforms to the target resistance, is provided.
In this method, the resistance at each means for heating increases as the temperature of the means for heating increases. As a result, as in the first aspect of the invention, temperature control on each means for heating is implemented based upon the corresponding actual resistance determined in conformance to the feedback voltage and the feedback current at the means for heating. Consequently, accurate temperature management is achieved for each means for heating. In addition, according to the present invention, the reference resistance is corrected based upon the detected temperature, as in the invention disclosed in claim 1. Thus, more accurate temperature control is achieved. Furthermore, the target resistance is obtained by multiplying the corrected reference resistance by a temperature distribution constant. Thus, even when heating the object to be heated with a plurality of means for heating, a consistent temperature distribution is achieved at the object to be heated in conformance to the current state of the object to be heated, as in the invention disclosed in claim 1.
It is desirable that in the step for power control, phase control is implemented on the power applied to each means for heating. By adopting such a method, the temperatures of the means for heating are adjusted through phase control as explained in reference to the previous aspects of the invention. As a result, the temperatures at the means for heating can be set with a high degree of accuracy.
Furthermore, it is desirable that the step in which phase control is implemented on the power include a step in which the length of time over which power is applied is increased if the actual resistance is smaller than the target resistance, a step in which the current length of power application is sustained if the actual resistance is essentially equal to the target resistance and a step in which the length of time over which power is applied is reduced if the actual resistance is higher than the target resistance. Through this method, the object to be heated can be set at a specific temperature with a high degree of reliability, as in the first aspect of the invention.
Alternatively, in the step for power control, zero cross control may be implemented on the power applied to each means for heating.
By adopting this method, it is ensured that noise is less likely to occur in the power applied to the means for heating, as in the previous aspect of the invention. As a result, power at a specific level is supplied in a stable manner.
As a desirable alternative, linear control may be implemented on the power supplied to each means for heating in the step for power control. Through such a method, the power can be controlled continuously, as in the previous aspects of the invention. As a result, better control is achieved.
Moreover, it is desirable to include a step in which the power supply to a means for heating is suspended if the actual resistance becomes higher than the resistance upper limit or the actual resistance becomes lower than the resistance lower limit. By adopting this method, an error at the means for heating can be detected based upon the actual resistance without having to provide a means for temperature detection that detects a temperature abnormality at the means for heating, as explained earlier in reference to the first aspect of invention. Thus, damage to the object to be heated and the like can be prevented.
Also, it is desirable that the object to be heated is a member constituting a semiconductor manufacturing apparatus and the like. In such a case, the temperature control on the semiconductor manufacturing apparatus and the like can be implemented in an ideal state, as in the previous aspects of the invention.
In a fourth aspect of the present invention, a temperature control method to be implemented on a means for heating that heats an object to be heated comprising a step in which a reference voltage determined based upon the set temperature for the object to be heated is corrected by using a correction value obtained in correspondence to the temperature of the object to be heated detected by, at least, one means for temperature detection, a step in which the corrected reference voltage is multiplied by a temperature distribution constant used to adjust the temperature distribution of the object to be heated, which is determined in advance for each of at least two means for heating each with a resistance that increases in correspondence to a temperature increase to obtain a target voltage for each of the means for heating, a step in which the actual voltage applied to each of the means for heating is detected and a step in which the power applied to each means for heating is controlled so that the actual voltage at the means for heating conforms to the target voltage, is provided.
According to the present invention, each means for heating is controlled by using the corresponding actual voltage detected at the means for heating, as in the second aspect of the invention. Thus, it is not necessary to provide a means for actual voltage calculation or to implement an arithmetic operation step to calculate the actual voltage, to achieve simplification in the apparatus structure and simplification in the control process.
As in the preceding aspects of the invention, it is desirable that in the step for power control, phase control is implemented on the power applied to each means for heating. As in the preceding aspects of the invention, it is desirable that the step in which phase control is implemented on the power include a step in which the length of time over which power is applied is increased if the actual voltage is lower than the target voltage, a step in which the current length of power application time is sustained if the actual voltage is essentially equal to the target voltage and a step in which the length of time over which power is applied is reduced if the actual voltage is higher than the target voltage.
As an alternative, in the power control step, zero cross control may be implemented on the power applied to each means for heating or linear control may be implemented on the power applied to each means for heating, as in the preceding aspect of the invention.
As in the preceding aspects of the invention, it is desirable to include a step in which power supply to a means for heating is suspended if the actual voltage becomes higher than the voltage upper limit or the actual voltage becomes lower than the voltage lower limit.
As in the preceding aspects of the invention, it is desirable that the object to be heated is a member constituting a semiconductor manufacturing apparatus and the like.